What happened. Be descriptive; if we have to guess at what happened, we may not make the correct updates, and things won't work.

How do I locate my network information?

Windows XP
Click Start > Run > type 'cmd' and press enter. In the command prompt window that opens type ipconfig /all and press enter. Find the information listed under the correct adapter, (likely called Local Area Connection) and locate the Physical Address and IPv4 Address. These are the Ethernet Number (MAC address or Physical Address) and IP number/address respectively.

Windows Vista/7
Click Start, type cmd in the start search box above the start button and press enter. In the command prompt window that opens type ipconfig /all and press enter. Find the information listed under the correct adapter, (likely called Local Area Connection) and locate the Physical Address and IPv4 Address. These are the Ethernet Number (MAC address or Physical Address) and IP number/address respectively.

Mac OS X
Click on the Apple menu in the upper left corner. Click on Location > Network Preferences... In the left column, select Ethernet and click on Advanced in the lower right corner. The IP number/address is listed under the TCP/IP tab. The Ethernet Number (MAC address or Physical Address) is listed under the Hardware or Ethernet tab.